diff --git a/nix/nixos-module/collectd/dhcpcount.rb b/nix/nixos-module/collectd/dhcpcount.rb
index d7ef59d..7bd6b24 100755
--- a/nix/nixos-module/collectd/dhcpcount.rb
+++ b/nix/nixos-module/collectd/dhcpcount.rb
@@ -10,13 +10,15 @@ STDOUT.sync = true
 loop do
   seen = {}
   count = 0
-
-  header = nil
+  now = Time.now.to_i
 
   CSV::readlines("/var/lib/kea/kea-leases4.csv", headers: true).each do |rec|
     h = rec.to_h
     addr = h["hwaddr"]
     next unless addr
+    last = h["expire"].to_i
+    elapsed = now - last
+    next if elapsed >= TIMEOUT
 
     unless seen[addr]
       count += 1
diff --git a/nix/nixos-module/container/dhcp-server.nix b/nix/nixos-module/container/dhcp-server.nix
index cbb6fbc..3321ed0 100644
--- a/nix/nixos-module/container/dhcp-server.nix
+++ b/nix/nixos-module/container/dhcp-server.nix
@@ -50,6 +50,7 @@ in
           code = 6;
           data = "172.20.73.8, 9.9.9.9";
         } ];
+        ddns-qualifying-suffix = domainName;
       });
 
       match-client-id = false;